Head and neck squamous cell carcinoma (
HNSCC) is a major public health concern. The recent identification of the mTOR complex 1 (
mTORC1) signaling pathway as a highly prevalent molecular signature underlying
HNSCC pathogenesis has provided the foundation to search for novel therapeutic approaches to prevent and treat
HNSCC. Here, we asked whether
metformin, the most widely used medication for the treatment of type II diabetes, which acts in part by stimulating the
AMP-activated protein kinase (AMPK) signaling pathway thereby reducing
mTORC1 activity, may lower the risk of
HNSCC development. Indeed, we show that
metformin reduces the growth of
HNSCC cells and diminishes their
mTORC1 activity by both AMPK-dependent and -independent mechanisms. We also optimized an oral-specific
carcinogenesis mouse model that results in the accumulation of multiple oral premalignant lesions at the end of the
carcinogen exposure, some of which then spontaneously progress into
HNSCC. Using this mouse model, we observed that
metformin specifically inhibits
mTORC1 in the basal proliferating epithelial layer of oral premalignant lesions. Remarkably,
metformin prevented the development of
HNSCC by reducing significantly the size and number of
carcinogen-induced oral tumoral lesions and by preventing their spontaneous conversion to
squamous cell carcinomas. Collectively, our data underscore the potential clinical benefits of using
metformin as a targeted chemopreventive agent in the control of
HNSCC development and progression.